7.
如图,在矩形ABCD中,AB=5,BC=6,点E,F,G,H分别在已知矩形的四条边上,且四边形EFGH也是矩形,GF=2EF.若设AE=a,AF=b,则a与b满足的关系为( )
| A. | $\left\{\begin{array}{l}{a+b=5}\\{a+2b=6}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{a=2b}\\{2a+b=6}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{2a+b=5}\\{a+2b=6}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{2a+b=6}\\{a+2b=5}\end{array}\right.$ |
6.若x<0,则化简$\sqrt{{-x}^{3}y}$的结果是( )
| A. | -x$\sqrt{xy}$ | B. | x$\sqrt{-xy}$ | C. | -x$\sqrt{-xy}$ | D. | x$\sqrt{xy}$ |
5.下列式子为最简二次根式的是( )
0 305822 305830 305836 305840 305846 305848 305852 305858 305860 305866 305872 305876 305878 305882 305888 305890 305896 305900 305902 305906 305908 305912 305914 305916 305917 305918 305920 305921 305922 305924 305926 305930 305932 305936 305938 305942 305948 305950 305956 305960 305962 305966 305972 305978 305980 305986 305990 305992 305998 306002 306008 306016 366461
| A. | $\sqrt{\frac{x}{2}}$ | B. | $\sqrt{27}$ | C. | $\sqrt{{x}^{2}-4}$ | D. | $\sqrt{{2x}^{2}y}$ |